震陷场地变截面单桩动力特性与损伤评价

Dynamic characteristics and damage evaluation of variable-section single pile in a seismic subsidence site

为探明震陷场地变截面单桩动力响应特性与损伤状况,以翔安大桥为工程背景,基于大型振动台试验,开展了0.10g~0.45g地震动强度下变截面单桩动力响应特性的研究,评价分析了变截面单桩损伤程度。结果表明:受桩周软弱土层震陷特性的影响,变截面单桩桩顶水平位移动力响应、桩身加速度动力响应及桩身弯矩动力响应均随地震动强度增大呈增大趋势,桩基基频逐渐减小;变截面单桩弯矩最大值出现在震陷土层分界处,地震动强度为0.30g时,超过了其抗弯承载力;地震动强度为0.20g时,变截面单桩桩顶水平位移、桩身加速度、桩身弯矩显著增大,桩基基频突降。基于系统损伤理论,震陷场地变截面单桩损伤状况分为稳定阶段、加剧损伤阶段、塑性破坏阶段共3个阶段。试验结束后,变截面位置处产生弯曲塑性破坏。

s:Investigating the dynamic response and damage condition of variable-section single pile in seismic subsidence site,taking Xiang’an Bridge as the engineering background,the dynamic response of variable-section single pile under 0.10g–0.45g ground vibration intensity was investigated through large shaking table tests,and the damage degree was evaluated and analyzed.Results are as follows:Influenced by the seismic subsidence characteristics of the soil layer,the top horizontal displacement,acceleration,and bending moment of the variable-section single pile tend to increase with the increase of vibration intensity,while the base frequency of the variable-section single pile gradually decreases.The maximum bending moment of the variable-section single pile occurs at the seismic subsidence soil stratum demarcation,where the ground shaking strength of 0.30g exceeds its flexural capacity.At a ground vibration intensity of 0.20g,the top horizontal displacement,acceleration,bending moment of the variable-section single pile increase significantly,and the base frequency of the pile decreases abruptly.Based on the system damage theory,the damage condition of variable-section single piles in seismic subsidence sites can be divided into three stages:stable stage,intensified damage stage,and plastic failure stage.At the end of the test,bending plastic damage occurred at the location of the variable section.